1. Field of the Invention
The present invention relates to a structure and method for the affixing of a pretensioner gas generator used in seat belt devices fitted in vehicles such as cars.
2. Description of the Related Art
Seat belt devices are provided in vehicles such as cars as means for protecting the passenger at moments of sudden acceleration or deceleration. The modern seat belt device comprises a pretensioner for, when the vehicle is subject to impact such as at moments of collision, retracting the seat belt further than the state in which it has been fastened by the passenger and restraining the passenger against the seat belt with a powerful force.
Although a range of systems of pretensioner are available, one such system is a gas pressure-type pretensioner comprising a gas generator that generates a high-pressure gas at the moment of collision of the car, a driving member such as balls or the like that retract the seat belt around a retractor, and a pipe that leads the high-pressure gas from the gas generator to the driving member (see, for example, Japanese Patent Application Laid-open No. 2001-63519).
In pretensioners of a structure such as this, generally, the end part of the pipe in which the driving member such as a balls are housed is expanded to form a housing part for the gas generator, a gas generator is fitted into the housing part through an opened end of the housing part, and the gas generator is held in the end part of the pipe by the calking of the opened end of the housing part (see, for example, Japanese Patent Application Laid-open No. 2002-331911).
However, with improved safety in mind, the trend in recent years has been towards further increases in the seat belt retracting force produced by the above mentioned pretensioners.
However, there have been instances where gas generators with an increased amount of explosive held in pipes of the prior art where the end part of the pipe, that is to say, the calked part, has broken due to the explosive force generated by the gas generator resulting in the detachment of the gas generator.
Although, as a countermeasure for this, the installation of a separate component part in the pipe and affixing of the gas generator using this separate component part has been considered, this has an associated unavoidable cost increase. In addition, although the thickening of the thickness of the wall of the pipe and the increasing of the strength of the calked part have been considered, these measures invite the increased weight of the pretensioner and a greater complexity of the machining thereof and, naturally, these also lead to a cost increase.